The present invention relates to a bending device for bending a pipe, a molding of an automobile window frame, a window frame sash and other elongate materials having various cross-sectional configurations.
A heretofore known bending device is, as disclosed in a publication of Japanese Patent Application No. Hei 1-154824, provided with a positioning jig with a clearance formed therein for passing an elongate material a bending jig having a clearance formed therein for passing the material supplied from the positioning jig, and for bending the material by moving the bending jig in a plane perpendicular to a material supply direction.
In this conventional bending device, as shown in FIGS. 6A and 6B, a material 100 being supplied is bent to a predetermined bend radius by moving a bending jig 102. At the start of a bending process, when a bent portion of the material 100 is supplied to the bending jig 102, the bending jig 102 is moved to a position in accordance with the bend radius. Subsequently, the bending jig 102 is moved back to a position coaxial with a positioning jig 104, thereby ending the bending process. As shown in FIG. 6A, at the start of the bending process, while the bending jig 102 is moving, a bend radius of the material 100 is changed from a radius R1 to a smaller radius R2. Subsequently, as shown in FIG. 6C, when the bending jig 102 reaches a position corresponding to a bend radius R3, the bending jig 102 stops moving to bend the material 100 to the predetermined bend radius.
Subsequently, when the bending jig 102 is moved back to its original position, the bend radius will change to a larger bend radius. As a result, especially when the material is bent to a small bend radius, the bend radius changes substantially between the start and the end of the bending process.
In another conventional bending device there is provided a rotary plate on which a bending jig is rotatably supported. While supplying the material, the material is bent by moving the bending jig in a plane perpendicular to a material supply direction, and twisted by rotating the rotary plate about the material. In this conventional bending device, to rotatably support the rotary plate centered on the material, a rotation axis of the rotary plate needs to be rotatably supported by plural rollers and mechanism is unduly complicated.